This invention relates to a vented paint cup or container for a suction feed hand held paint spray gun and more particularly to an improved tortuous passage vent structure which eliminates dripping from the paint cup vent as the spray gun is tilted during operation and is easily cleaned after use.
In one commonly used type of spray gun, compressed air is supplied through the spray gun to a nozzle. As the compressed air flows through the spray gun, suction resulting from the flow of the air to the nozzle draws paint from a paint cup and carries the paint to the nozzle where the air and entrained paint are discharged. As the paint is discharged from the nozzle, the air breaks up and atomizes the paint and carries the paint towards a workpiece for coating the workpiece. In order to apply a quality coating, it is necessary to maintain the spray gun perpendicular to the surface being coated. When workpiece surfaces have different configurations, it is necessary to tilt the spray gun in order to maintain the spray gun perpendicular to the workpiece surface. In order to prevent paint from dripping from the paint cup onto the workpiece as the spray gun is tilted and moved, the paint cup is sealed. However, the paint cup must be vented to equalize the pressure within the paint cup as paint is consumed. Without a vent, a vacuum will build up within the paint cup as paint is consumed and eventually paint flow to the nozzle will cease.
Various vent structures have been used in the past for allowing the air pressure within the paint cup to equalize with the atomosphere. The simplest structure is merely a vent hole formed in the paint cup lid. Such an arrangement works quite well provided that the paint cup is not tilted to the point that the vent opening is below the paint surface level within the paint cup. If the spray gun is tilted to the point that the vent opening is below the surface level, dripping may occur and if paint drips onto the workpiece the surface finish will be damaged. Various improvements have been made on this simple vent structure including the provision of a check valve within the vent opening or the provision of a vent passage which forms a tortuous path. When a tortuous path has been provided for the vent opening, the passages are often very small and difficult to clean. One vent of this type comprises a curved tube which lies within the paint cup lid. The vent tube must be removed from the lid for cleaning. Even when the tube is removed, only the ends of the tube provide access for cleaning.